Coagulation active proteins are considered suitable for the treatment of blood coagulation disorders. In other contexts, such proteins can be used to make antibodies for a variety of uses.
Turning to the coagulation disorders themselves, such disorders are found where the coagulation time deviates from the standard value due to the lack of a coagulation component. The disorders can be inherited as well as acquired through disease conditions.
Hemophilia A is one of the most frequently occurring inherited coagulation disorders. Patients with hemophilia A are prone to frequent hemorrhages as a result of a lack of Factor VIII which can be treated with Factor VIII concentrates. However, in about 15% of the patients Factor VIII neutralizing antibodies, so-called inhibitors, occur, which greatly limits the usefulness of Factor VIII concentrates.
For the treatment of hemophilia A inhibitor patients, complex mixtures of coagulation factors have been employed. The activated prothrombin complex FEIBA.RTM. (Immuno) has a "factor eight inhibitor bypassing activity".
In lieu of Factor VIII concentrates, it has been attempted to treat hemophilia A with a mixture of coagulation factor Xa and phospholipids. In U.S. Pat. No. 4,610,880, the treatment of hemophilic dogs with a mixture of Factor Xa and phospholipid vesicles is described. This mixture was not stable, and therefore a Factor Xa-containing solution and a suspension of phospholipid vesicles had to be freshly mixed immediately prior to use. It is stressed that the mixture ratio must be selected in such a way that hemostasis is achieved without causing thromboses.
It is known that combined administration of phospholipid vesicles with Factor Xa, wherein the vesicles and Factor Xa are not bound to one another, increases the danger of thrombosis. On the basis of an in vivo stasis model with rabbits in Blood 59, 401-407 (1982), the increased thrombogenicity of Factor Xa is described when it was tested together with synthetic phospholipids (phosphatidyl choline/phosphatidyl serine lipid vesicles, PCPS vesicles). The danger of thrombosis after administration of prothrombin complex concentrates also is attributed to the combination of coagulation active phospholipids and activated coagulation factors.
It is known from U.S. Pat. No. 4,348,384 to incorporate the coagulation factors Factor VIII and IX inside liposomes. Therewith, a preparation which can be orally or intestinally administered for the treatment of Hemophilia A or B is made available. Here, the liposomes have a size of 1 .mu.m and protect the Factor VIII or Factor IX from a premature digestion. The administration of these preparations holds no danger of thrombosis because it does not occur intravenously.
The instability of activated coagulation factors in storage is known. A. method is known from Thrombosis Research 22: 213-20 (1981) which permits an as stable as possible beta-Factor Xa preparation to be obtained. According to this method, beta-Factor Xa is stored refrigerated in 50% glycerin at pH 7.2 in 0.03 M imidazole buffer. However, a further conversion to inactive fragments also occurs in this method even at 4.degree. C. In a similar manner, the instability of Factor Xa in stabilizing glycerol-water mixtures also is described in J. Biol. Chem. 248: 7729-41 (1973).
The combined administration of Factor Xa with liposomes as separate entities also is know. See Giles et al., U.S. Pat. No. 4,721,618. Giles explains that the mixing must be done immediately prior to administration. See Giles at column 5, lines 7-9. Prior to mixing, Giles stores Factor Xa in a 50% glycerol solution at -20.degree. C. See column 4, lines 41-42. The phospholipid vesicles are stored at 4.degree. C. See Giles at column 4, line 62 to column 5, line 3. Giles thus does not disclose binding Factor Xa to a lipid vesicle in order to from a storage-stable preparation.